Vobla - Back up your Linux servers continuously
Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
Examdiff Pro - It is a simple yet powerful tool that is being used by the professional programmer and developers for the purpose of visual comparison.
UptimeRobot App - Web, SSL, ports & Cron-jobs monitoring
Dead Man's Snitch - Monitor Cron Jobs and Windows Scheduled Tasks with ease.
Cronitor - Monitor cron jobs, micro-services, daemons and almost anything else, no setup required. Easier cron troubleshooting and no more silent failures.